High strength vibrational-dampened components

ABSTRACT

An article that includes a polymer-based substrate; and a metallic nano-crystalline coating on at least a portion of the polymer-based substrate, where the metallic nano-crystalline coating defines an average grain size less than about 20 nanometers, where the portion of the polymer-based substrate has a first Young&#39;s modulus and the metallic nano-crystalline coating has a second Young&#39;s modulus, where the first Young&#39;s modulus is at least five times less than the second Young&#39;s modulus.

This application claims the benefit of U.S. Provisional Application No. 62/310,367 filed Mar. 18, 2016, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates techniques for forming high strength metal-polymer articles for use in aerospace componentry.

BACKGROUND

Aerospace components are often operated in relatively extreme environments that may expose the components to a variety of stresses or other factors including, for example, thermal cycling stress, shear forces, compression/tensile forces, vibrational/bending forces, impact forces from foreign objects, erosion and corrosion, and the like. The exposure of the aerospace components to the variety of stresses, forces, and other factors may impact the lifespan of the component, such as leading to early fatigue or failure. In some examples, aerospace components have been developed that exhibit higher strength and durability using high density metals or metal alloys. However, some high density metals or metal alloys may be relatively heavy, difficult to manufacture, and expensive making their use non-ideal for aerospace applications.

SUMMARY

In some examples, the disclosure describes an article that includes a polymer-based substrate; and a metallic nano-crystalline coating on at least a portion of the polymer-based substrate, where the metallic nano-crystalline coating defines an average grain size less than about 20 nanometers, where the portion of the polymer-based substrate has a first Young's modulus and the metallic nano-crystalline coating has a second Young's modulus, where the first Young's modulus is at least five times less than the second Young's modulus.

In some examples, the disclosure describes an article that includes a polymer-based substrate and a metallic nano-crystalline coating on at least a portion of the polymer-based substrate, where the metallic nano-crystalline coating defines an average grain size less than about 20 nanometers, where the portion of the polymer-based substrate has a first Young's modulus and the metallic nano-crystalline coating has a second Young's modulus, and where the first and second Young's modulus are selected to dampen a predetermined vibration frequency in the article.

In some examples, the disclosure describes a method for forming an aerospace component that includes forming a polymer-based substrate comprising a polymeric material and depositing a metallic nano-crystalline coating on at least a portion of the polymer-based substrate, where the metallic nano-crystalline coating defines an average grain size less than about 20 nanometers, where the portion of the polymer-based substrate defines a first Young's modulus and the metallic nano-crystalline coating has a second Young's modulus, where the first and second Young's modulus are selected to dampen a vibration in the article at a predetermined frequency.

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a conceptual perspective view of an example component that includes a nano-crystalline coating applied to a polymer-based substrate.

FIG. 1B is a cross-sectional view of the component of FIG. 1A along line A-A.

FIG. 2 is a conceptual cross-sectional view of an example article including polymer-based substrate and plurality of metallic nano-crystalline layers.

FIG. 3 is a conceptual cross-sectional view of an example article that includes a metal-polymer laminate on a portion of a polymer-based substrate.

FIG. 4A is conceptual cross-sectional view of an example article that includes a metallic nano-crystalline coating on at least a portion of a polymer-based substrate that includes a selectively varied Young's modulus.

FIG. 4B is conceptual cross-sectional view of an example article that includes a metallic nano-crystalline coating on at least a portion of a polymer-based substrate that includes a polymeric material and a plurality of reinforcement fibers.

FIG. 5A is a conceptual perspective view of an example component that includes a dense core material, a polymer-based substrate, and a metallic nano-crystalline coating deposited on at least a portion of polymer-based substrate.

FIG. 5B is a cross-sectional view of the component of FIG. 5A along line B-B.

FIG. 6 is a conceptual cross-sectional view of an example component that includes a trussed polymer-based substrate.

FIG. 7 is a flow diagram illustrating an example technique for forming an example article that includes a metallic nano-crystalline coating on a polymer-based substrate.

DETAILED DESCRIPTION

In general, the disclosure describes aerospace components and techniques for making aerospace components that include a polymer-based substrate having a high strength metallic nano-crystalline coating applied to at least a portion of the polymer-based substrate. The techniques described herein may be used to form aerospace components that exhibit improved strength and reduced weight characteristics compared to conventional titanium, steel, or other high density metal components. Additionally or alternatively, the described techniques may be used to form aerospace components with improved noise and vibrational dampening characteristics which may result in an increased service life for the component. In some examples, the components may be constructed such that the Young's modulus of the metallic nano-crystalline coating and the Young's modulus of the polymer-based substrate are configured to dampen a vibration in the component at a predetermined frequency or frequency range (e.g., frequencies to which the component is exposed during operation. In some examples, the predetermined frequency range may be between 500 Hertz (Hz) and about 5,000 Hz. In some examples, the vibrational-dampening effect may be obtained by selecting the Young's modulus of the polymer-based substrate to be at least five times less than the Young's modulus of the metallic nano-crystalline coating.

FIG. 1A is a conceptual perspective view of an example component 10 that includes a nano-crystalline coating 14 applied to a least a portion of a polymer-based substrate 12. FIG. 1A includes a cutout section 16 that reveals polymer-based substrate 12. FIG. 1B provides an alternative cross-sectional view of component 10 of FIG. 1A along line A-A.

In some examples, the conditions in which component 10 is typically operated (e.g., aerospace applications), may exert one or more vibrational forces on the article. Depending on the structure and natural resonance frequency of component 10, the applied vibrational forces may be similar to the natural resonance frequency of component 10, thereby causing the article to resonate. The resonance of component 10 may lead to increased noise and, over an extended period of time, may cause early fatigue of the component. The applied vibrational forces are a particular concern for turbine engine components and external aircraft components where the parts are subjected to turbulent air flow which can generate the described vibrational forces, or vibrations from other components (e.g., combustor, driveshafts, and the like). In such instances, it may be desirable for component 10 to possess a natural resonance frequency outside the range or otherwise dampen the vibrational frequencies anticipated to be exerted on the component during operation.

In some examples, component 10 may be constructed such that the Young's modulus of polymer-based substrate 12 and metallic nano-crystalline coating 14 are configured to dampen a vibration in the component at a predetermined frequency or frequency range (e.g., the vibrational frequencies exerted on component 10 during operation). For example, polymer-based substrate 12 may possess a Young's modulus substantially less than the Young's modulus of metallic nano-crystalline coating 14 (e.g., a Young's modulus as measured in pascals (Pa) of at least 5 times less than that of metallic nano-crystalline coating 14).

In some examples, having a Young's modulus in polymer-based substrate 12 substantially less than metallic nano-crystalline coating 14 may improve the vibrational dampening characteristics of component 10. For example, without wanting to be bound to a specific scientific theory, the lower Young's modulus of polymer-based substrate 12 compared to metallic nano-crystalline coating 14 may allow for relative motion between polymer-based substrate 12 and metallic nano-crystalline coating 14 during operation of component 10. The relative motion may allow for the vibrations exerted on component 10 during operation to be dissipated by the relative motion, resulting in improved vibrational dampening properties of component 10. Additionally or alternatively, the relatively low Young's modulus of polymer-based substrate 12 may help alter the natural resonance frequency of component 10, such that the natural resonance frequency of component 10 lies outside the range of vibrational frequencies anticipated during operation.

In some examples, the Young's modulus of polymer-based substrate 12 or metallic nano-crystalline coating 14 may be determined using suitable standardized techniques including, for example, ASTM test method E2769. In some examples, polymer-based substrate 12 may be configured to have a Young's modulus less than about 4 giga pascals (GPa) while metallic nano-crystalline coating 14 may possess a Young's modulus greater than about 200 GPa.

Polymer-based substrate 12 may include any suitable polymeric material. In some examples, the polymeric material may include, for example, polyether ether ketone (PEEK), polyamide (PA), polyimide (PI), bis-maleimide (BMI), epoxy, phenolic polymers (e.g., polystyrene), polyesters, polyurethanes, silicone rubbers, copolymers, polymeric blends, and the like. In some examples, the polymeric material may be combined with one or more optional additives including, for example, binders, hardeners, plasticizers, antioxidants, and the like.

In some examples, in addition to the polymeric material, polymer-based substrate 12 may also include one or more reinforcement fibers/materials including, for example, carbon fibers, carbon nano-tubes, and the like embedded in the polymeric material. The presence reinforcement fibers/materials in the polymeric material may increase the relative strength of polymeric material, thereby increasing the strength of the resultant polymer-based substrate 12 in addition to increasing the Young's modulus of the resultant substrate. In some examples, polymer-based substrate 12 may include between about 10% to about 40% reinforcement fibers/materials (e.g., carbon fibers) mixed with polymeric material and the one or more optional additives. In other examples, polymer-based substrate 12 may consist essentially of polymeric material.

Polymer-based substrate 12 may be formed using any suitable technique. For example, polymer-based substrate 12 may be formed using a mold process in which molten polymeric material may be combined with optional additives or reinforcement materials and cast into a three-dimensional mold to form polymer-based substrate 12 with the desired shape. In some examples, polymeric material may be injected into a mold containing structure reinforcement fibers wherein polymeric material encases and solidifies around the reinforcement fibers to form polymer-based substrate 12 with the desired shape. In other examples, polymer-based substrate 12 may be fabricated as a sheet/foil, which may be substantially planar (e.g., planar or nearly planar) or sculpted into a desired shape (e.g., a panel in the shape of the leading edge of an airfoil).

Metallic nano-crystalline coating 14 of component 10 may include one or more layers of metals or metal alloys that defines an ultra-fine-grained microstructure with an average grain size less than about 50 nanometers (nm), e.g., less than 20 nm. In some examples, the reduced grain size of metallic nano-crystalline coating 14 may increase the relative tensile strength of the resultant layer as well as the overall hardness of the layer, such that metallic nano-crystalline coating 14 may be significantly stronger and more durable compared to a conventional metallic coating (e.g., coarse grain coating) of the same composition and thickness. In some examples, the increased strength and hardness of metallic nano-crystalline coating 14 may allow for the layer to remain relatively thin (e.g., between about 0.025 millimeters (mm) and about 0.15 mm) without sacrificing the desired strength and hardness characteristics of the layer. Additionally or alternatively, depositing a relatively thin layer of metallic nano-crystalline coating 14 on polymer-based substrate 12 may help reduce the overall weight of component 10 by reducing the volume of denser metals or metal alloys. The combination of the relatively light weight polymer-based substrate 12 and metallic nano-crystalline coating 14 may result in a relatively high strength, relatively low weight article ideal for aerospace components.

Metallic nano-crystalline coating 14 may define an ultra-fine-grained microstructure having average grain sizes less than about 50 nm. In some examples, the average grain size of metallic nano-crystalline coating 14 may be less than about 20 nm, such as less than about 5 nm. Metallic nano-crystalline coating 14 may include one or more pure metals or metal alloys including, for example, cobalt, nickel, copper, iron, cobalt-based alloys, nickel-based alloys, copper-based alloys, iron-based alloys, or the like deposited on at least a portion of polymer-based substrate 12. In some examples, the metal or metal alloy may be selected so that metallic nano-crystalline coating 14 possesses a Young's modulus greater than about 200 GPa.

Metallic nano-crystalline coating 14 may be formed using suitable plating techniques, such as electro-deposition. For example, polymer-based substrate 12 may be suspended in suitable electrolyte solution that includes the selected metal or metal alloy for metallic nano-crystalline coating 14. A pulsed or direct current (DC) may then be applied to polymer-based substrate 12 to plate the substrate with the fine-grained metal to form metallic nano-crystalline coating 14 to a desired thickness and average grain size. In some examples a pulsed current may be utilized to obtaining an average grain size less than about 20 nm.

In some such examples, polymer-based substrate 12 may be initially metalized in select locations with a base layer of metal to facilitate the deposition process of forming metallic nano-crystalline coating 14 on polymer-based substrate 12 using electro-deposition. In some examples, the metalized base layer on polymer-based substrate 12 may be produced using, for example, electroless deposition, physical vapor deposition (PVD), chemical vapor deposition (CVD), cold spraying, gas condensation, and the like. The layer formed using metallization may include one or more of the metals used to form metallic nano-crystalline coating 14.

In some examples, metallic nano-crystalline coating 14 may be configured to exhibit improved barrier protection against erosion or corrosion compared to traditional materials used for aerospace components. For example, metallic nano-crystalline coating 14 may include a layer of nano-crystalline cobalt. The layer of nano-crystalline cobalt may impart anti-corrosion properties to component 10 as well as increased friction resistance and wear resistance to metallic nano-crystalline coating 14 compared to traditional materials used for aerospace components.

Additionally or alternatively, metallic nano-crystalline coating 14 may be configured to contribute to the durability of component 10 to resist impact damage from foreign objects during operation. For example, to improve impact damage resistance against foreign objects, aerospace components have traditionally been formed or coated with high strength metals such as titanium. Such techniques, however, may suffer from increased costs associated with processing and raw materials. Additionally, components formed from high strength metals such as titanium tend to result in relatively dense and heavy components which may be less desirable in aerospace applications. Forming component 10 to include polymer-based substrate 12 and metallic nano-crystalline coating 14 (e.g., nano-crystalline nickel) may significantly reduce the weight of the component compared to those formed with traditional high strength metals (e.g., titanium) while also obtaining comparable or even improved impact damage resistance characteristics.

In some examples, the thickness 18 of metallic nano-crystalline coating 14 may be between about 0.025 mm and about 0.15 mm. In some examples, metallic nano-crystalline coating 14 may be about 0.13 mm (e.g., about 0.005 inches). In some examples, the overall thickness 18 of metallic nano-crystalline coating 14 may be selectively varied on different portions of polymer-based substrate 12 to withstand various thermal and mechanical loads that component 10 may be subjected to during operation. For example, in areas where increased impact damage resistance is desired, e.g., the leading edge of a turbine blade, the relative thickness of metallic nano-crystalline coating 14 may be increased to impart greater strength properties in that region. Additionally or alternatively, thickness 18 of metallic nano-crystalline coating 14 in regions where increased impact damage resistance is less desired, the thickness of the coating may be reduce or removed from component 10.

As shown in FIG. 1A, in some examples, component 10 may be in the form of an aerospace component such as a turbine engine blade. However, component 10 may include any number of aerospace components that may benefit from the described strength characteristic, reduced weight, or vibrational dampening features. Other aerospace components may include, for example, housings, brackets, air ducts, manifolds, tubes, chevron ventilation outlets, vane box plume tabs, variable vane actuator arms, nose cones, transition duct seals, actuation rings, airfoils, flaps, casing, frames, accessory gear, drive shafts, rotors, discs, panels, tanks, covers, flow surfaces, turbine engine components, and the like. In some examples, component 10 may exhibit complex three-dimensional geometries such as a turbine engine blade. In other examples, component 10 may be in the form of a sheet or a shaped-sheet component used such as airfoil, air flow surface, or housing component.

In some examples, metallic nano-crystalline coating 14 may include a plurality of metallic nano-crystalline layers. FIG. 2 is a conceptual cross-sectional view of an example article 20 including polymer-based substrate 28 (e.g., similar to polymer-based substrate 12 as described above) and a metallic nano-crystalline coating 22 that includes a first metallic nano-crystalline layer 24 and a second metallic nano-crystalline layer 26.

In some examples, first and second metallic nano-crystalline layers 24 and 26 may be selectively tailored to produce a metallic nano-crystalline coating 22 with desired physical, thermal, and chemical (e.g., corrosion resistance) characteristics. For example, first metallic nano-crystalline layer 24 may include nano-crystalline nickel or nickel-based alloy which may impart high tensile strength properties to metallic nano-crystalline coating 22 to contribute to the overall durability of article 20. Second metallic nano-crystalline layer 26 may include nano-crystalline cobalt or a cobalt-based alloy, which may impart anti-corrosion properties to metallic nano-crystalline coating 22 as well as friction resistance and wear resistance.

In some examples, the relative thicknesses of first and metallic second nano-crystalline layers 24 and 26 may be substantially the same (e.g., the same or nearly the same) or may be different depending on the composition of the respective layer and intended application of article 20. In some examples in which first metallic nano-crystalline layer 24 includes nickel or a nickel-based alloy and second metallic nano-crystalline layer 26 includes cobalt or a cobalt-based alloy, the relative thicknesses of the layers may be selected such that first metallic nano-crystalline layer 24 is about three times thicker than second metallic nano-crystalline layer 26 (e.g., producing a thickness ratio of about 3:1 cobalt layer to nickel layer). For example, first metallic nano-crystalline layer 24 (which may include nickel or a nickel-based alloy) may have a thickness of about 0.025 mm (e.g., about 0.001 inches) to about 0.038 mm (about 0.0015 inches) and second metallic nano-crystalline layer 26 (which may include cobalt or a cobalt-based alloy) may have a thickness of about 0.075 mm (e.g., about 0.003 inches) to about 0.13 mm (about 0.005 inches) at about a 3:1 thickness ratio.

Additionally or alternatively, the article may be constructed with a multi-layered metal-polymer laminate structure. For example, FIG. 3 is a conceptual cross-sectional view of an example article 30 including polymer-based substrate 38 (e.g., similar to polymer-based substrate 12 as described above) and a metal-polymer laminate 36 on a portion of polymer-based substrate 38. Metal-polymer laminate 36 may include one or more polymer-based layers 34 and one or more metallic nano-crystalline layers (e.g., first metallic nano-crystalline layer 32 a and second metallic nano-crystalline layer 32 b; collectively “metallic nano-crystalline layers 32”) applied on polymer-based substrate 38 in an alternating fashion such that the outermost layer (e.g., layer 32 b) includes a metallic nano-crystalline layer. In some examples, the alternating configuration of the one or more metallic nano-crystalline layers 32 a and 32 b with one or more polymer-based layers 34 may impart additional vibrational-dampening properties to article 30 by allowing for additional relative motion between one or more of the adjacent layers (e.g., between polymer-based layer 34 and first metallic nano-crystalline layer 32 a, between polymer-based layer 34 and second metallic nano-crystalline layer 32 b, or both).

In some examples, the one or more metallic nano-crystalline layers 32 may include the substantially the same (e.g., the same or nearly the same) composition of metals. In other examples, metallic nano-crystalline layers 32 may include different compositions of metals to impart different characteristics to article 30. For example, second metallic nano-crystalline layers 32 b may include nano-crystalline cobalt or cobalt-based alloy, which may impart anti-corrosion properties to metal-polymer laminate 36 as well as contribute friction resistance and wear resistance to the laminate structure, and first metallic nano-crystalline layers 32 a may include nano-crystalline nickel or nickel-based alloy, which may impart high tensile strength properties to the laminate structure to improve the overall durability of article 30. In some examples, the thicknesses of first and second metal nano-crystalline layers 32 a and 32 b may be between about 0.025 mm (e.g., about 0.001 inches) to about 0.13 mm (about 0.005 inches). The thickness selected for a respective layer may depend on a variety of factors including, for example, the composition of the respective layer, the purpose of the respective layer, and the total number of layers in metal-polymer laminate 36. In some examples, metal-polymer laminate 36 may define an overall thickness of about 0.025 mm to about 0.15 mm.

The one or more polymer-based layers 34 may be formed using any suitable polymeric material. In some examples, one or more of polymer-based layers 34 may include substantially the same (e.g., the same or nearly the same) polymeric material or include a composition substantially the same (e.g., the same or nearly the same) as polymer-based substrate 38. Each respective layer of polymer-based layers 34 may be formed using any suitable technique including, for example, injection molding, dip coating, and the like. The thickness of each respective layer of polymer-based layers 34 may be between about 0.025 mm and about 0.15 mm.

In some examples, the polymer-based substrate may be configured to possess additional vibrational-dampening characteristics by selectively varying the Young's modulus within the polymer-based substrate by tailoring the composition of the polymer-based substrate within respective regions of the substrate. For example, FIG. 4A shows a conceptual cross-sectional view of an example article 40 that includes a metallic nano-crystalline coating 41 on at least a portion of a polymer-based substrate 42 a and 42 b (collectively “polymer-based substrate 42”) that includes two different regions (e.g., regions I and II). Within each region, the Young's modulus of the polymer-based substrate 42 may be selectively tailored by modifying the composition of the respective polymer-based substrate. For example, polymer-based substrate 42 a may be formulated to have a higher Young's modulus in region I compared to the Young's modulus of polymer-based substrate 42 b in region II.

FIG. 4B shows another example article 45 where the polymer-based substrate may be configured to possess additional vibrational-dampening characteristics by selectively varying the Young's modulus. FIG. 4B is a conceptual cross-sectional view of an example article 45 that includes a metallic nano-crystalline coating 48 on at least a portion of a polymer-based substrate 47 that includes a polymeric material 44 and a plurality of reinforcement fibers 46. Article 45 may be described in terms of one or more regions (e.g., regions I-III) having different relative concentrations of reinforcement fibers 46 embedded within polymeric material 44. In some examples, increasing the relative concentration of reinforcement fibers 46 in polymeric material 44 can increase the Young's modulus of polymer-based substrate 47 within the corresponding region compared to a region that includes the same polymeric material 44 and a lower concentration of reinforcement fibers 46. For example, due to the increased concentration of reinforcement fibers 46 within region II, region II may exhibit a higher Young's modulus compared to regions I and III, which possess a lower concentration of reinforcement fibers 46. In some examples, by varying Young's modulus within different regions of polymer-based substrate 47 by modifying the concentration of reinforcement fibers 46 within those regions, article 45 may exhibit increased vibrational dampening properties compared to a polymer-based substrate that has a uniform disbursement of reinforcement fibers 46 or otherwise homogenous composition.

In some examples, the vibrational dampening properties of component 10 may be further configured by including one or more dense core materials within the polymer-based substrate. For example, FIG. 5A is a conceptual perspective view of an example component 50 with a cutout revealing a dense core material 56 substantially encased by (e.g., encased or nearly encased) a polymer-based substrate 52, and a metallic nano-crystalline coating 58 deposited on at least a portion of polymer-based substrate 52. FIG. 5B is a cross-sectional view of component 50 of FIG. 5A along line B-B.

The relative density of dense core material 56 may be greater than the density of polymer-based substrate 52. In some examples, the density of dense core material 56 may be between about 2.5 grams per cubic centimeter (g/cm³) and about 9.0 g/cm³. In some examples, the relative weight of dense core material 56 compared the relative weight of polymer-based substrate 52, combined with the relatively low Young's modulus of polymer-based substrate 52 may allow for relative motion between dense core material 56 and polymer-based substrate 52 or between dense core material 56 and metallic nano-crystalline coating 54. The relative motion between dense core material 56 and the other components may impart additional vibrational-dampening properties to component 50.

In some examples, dense core material 56 may be a low cost metal substrate composed of a relatively low density metal or metal alloy including for example, aluminum, titanium, stainless steel, nickel, cobalt, and the like. In other examples, dense core material 56 may include a relatively high density polymer or polymer composites (e.g., HDPE).

Component 50 may be formed using any suitable technique. In some examples, dense core material 56 may be initially constructed to have a desired three-dimensional shape. For example, in some examples where dense core material 56 includes aluminum, dense core material 56 may be initially cast molded or machined from a block structure to produce a selected shape. Dense core material 56 may then be coated with polymer-based substrate 52 through, for example, a dip or injection molding process. Metallic nano-crystalline coating 54 may then be applied using pulsed electro-deposition as described above. In other examples, polymer-based substrate 52 may be initially formed using, for example, an injection molding process and, if needed, subsequently machined to include one or more internal cavities for receiving dense core material 56. The inner cavities of polymer-based substrate 52 may then be filled with dense core material 56 followed by the subsequent application of metallic nano-crystalline coating 54.

In some examples, the polymer-based substrate may be constructed as a truss structure. For example, FIG. 6 is a conceptual cross-sectional view of an example component 60 (e.g., along cross-section line A-A from FIG. 1A). Component 60 includes polymer-based substrate 62 and metallic nano-crystalline coating 14 on at least a portion of polymer-based substrate 62. Polymer-based substrate 62 may be formed with a plurality of truss connections 66 that form an exoskeleton structure defining a plurality of cavities 64. Polymer-based substrate 62, including truss connections 66, may include any suitable polymeric material or polymer composite material as discussed above.

The truss structure of polymer-based substrate 62 may be formed using any suitable technique including, for example, additive manufacturing, molding, and machining. In some examples, the truss structure of polymer-based substrate 62 in conjunction with metallic nano-crystalline coating 68 may allow for significant weight reduction of component 60 without significantly reducing the strength and durability properties of component 60. In some examples, one or more of the internal cavities 64 of polymer-based substrate 62 may be coated with one or more metallic nano-crystalline coatings (not shown) to further enhance the strength and durability properties of component 60 using, for example, the electrodeposition described above.

FIG. 7 is a flow diagram illustrating an example technique for forming an example article that includes a metallic nano-crystalline coating on a polymer-based substrate. While the techniques of FIG. 7 are described with concurrent reference to the conceptual diagrams of FIGS. 1-6, in other examples, the techniques of FIG. 7 may be used to form other articles and aerospace components, the articles and components of FIGS. 1-6 may be formed using a technique different than that described in FIG. 7, or both.

The technique of FIG. 7 includes forming a polymeric-based substrate 12 that includes a polymeric material (72) and depositing a metallic nano-crystalline coating 14 on at least a portion of the polymer-based substrate 12 (74). As described above, the polymeric material may include any suitable polymer including, for example, PEEK, PA, or the like. In some examples, as described above, polymer-based substrate 12 may be constructed to have a Young's modulus at least five times less than the Young's modulus metallic nano-crystalline coating 14. In some examples, the Young's modulus of polymer-based substrate 12 may be less than about 4 GPa.

In some examples, the polymer-based substrate (e.g., polymer-based substrate 47) may include a plurality of reinforcement fibers 46 embedded in a polymeric material 44. The presence reinforcement fibers 46 in polymer-based substrate 47 may increase the strength of the substrate in one or more selected regions. In some such examples, the Young's modulus of polymer-based substrate 47 may be selectively tailored in the one or more selected regions by altering the relative concentration of reinforcement fibers 46 within the different regions of polymer-based substrate 47 (e.g., regions I-III of FIG. 4B) to impart additional vibrational-dampening properties into the resultant article 45.

Polymer-based substrate 12 may be formed (72) using any suitable technique as described above. In some examples, polymer-based substrate 12 may be formed by an injection molding process to establish a desired three-dimensional structure.

In some examples, the polymer-based substrate (e.g., polymer-based substrate 52) may be formed to include one or more dense core materials 56 substantially encased (e.g., encased or nearly encased) within polymer-based substrate 52. In some such examples, the dense core material 56, may impart additional vibrational dampening characteristics into the final component 50 by permitting relative motion between the dense core material 56 and one or more of the polymer-based substrate 52 or metallic nano-crystalline coating 54.

Additionally or alternatively, the polymer-based substrate may be constructed as a truss structure (e.g., polymer-based substrate 62) that defines plurality of truss connections 66 and internal cavities 64 to form a lightweight exoskeleton structure. In some such examples, polymer-based substrate 62 may be formed by, for example, injection molding and/or machining polymer-based substrate 62 followed by application of metallic nano-crystalline coating 68 to the external surface of polymer-based substrate 62 and optionally one or more of the inner cavities 64 of polymer-based substrate 62 for increased strength.

The technique of FIG. 7 includes depositing a metallic nano-crystalline coating 14 on at least a portion of the polymer-based substrate 12 (74). As described above, metallic nano-crystalline coating 14 may include one or more layers of nano-crystalline metal (e.g., nickel, cobalt, copper, iron, or the like) or metal alloy (e.g., nickel-based alloy, cobalt-based alloy, copper-based alloy, iron-based alloy, or the like) that defines an ultra-fine-grained microstructure with an average grain size less than about 20 nanometers (nm). The metallic nano-crystalline coating 14 may be applied using an electro-deposition process (e.g., pulse electro-deposition using an electrolyte bath). In some examples, polymer-based substrate 12 may be initially metalized to aid in the deposition of metallic nano-crystalline coating 14.

In some examples, the metallic nano-crystalline coating may be deposited (74) as two or more metallic nano-crystalline layers with different metallic compositions. For example, as described with respect to FIG. 3, the metallic nano-crystalline coating 22 may include a first metallic nano-crystalline layer 24 including primarily nano-crystalline cobalt and a second metallic nano-crystalline layer 26 including primarily nano-crystalline nickel. In some examples, the two or more metallic nano-crystalline layers may be constructed to have differing thicknesses.

Additionally or alternatively, the metallic nano-crystalline coating may be deposited (74) as a metal-polymer laminate 36 that includes alternating layers of one or more metallic nano-crystalline layers 32 a and 32 b with one or more polymer-based layers 34. In some such examples, the metallic nano-crystalline layers 32 a and 32 b and polymer-based layers 34 may be selectively applied to allow for improved strength, wear and corrosion resistance, and additional relative motion between adjacent layers for increased vibrational-dampening properties.

In some examples, the overall thickness 18 of the metallic nano-crystalline coating 14 as measured normal to an exterior surface of the polymer-based substrate 12 may be selectively varied on different regions of polymer-based substrate 12 to tailor the strength, impact-resistance, corrosion-resistance, or other characteristics within the different regions of component 10.

Various examples have been described. These and other examples are within the scope of the following claims. 

What is claimed is:
 1. An article comprising: a polymer-based substrate; and a metallic nano-crystalline coating on at least a portion of the polymer-based substrate, wherein the metallic nano-crystalline coating defines an average grain size less than about 20 nanometers, wherein the portion of the polymer-based substrate has a first Young's modulus and the metallic nano-crystalline coating has a second Young's modulus, wherein the first Young's modulus is at least five times less than the second Young's modulus.
 2. The article of claim 1, wherein the polymer-based substrate comprises a plurality of reinforcement fibers embedded in a polymeric material.
 3. The article of claim 2, wherein the plurality of reinforcement fibers are non-uniformly distributed in the polymer-based substrate.
 4. The article of claim 1, further comprising a dense core material, wherein the polymer-based substrate substantially surrounds the dense core material.
 5. The article of claim 1, wherein the polymer-based substrate includes a polymeric material selected from the group consisting of polyether ether ketone (PEEK), polyamide (PA), polyimide (PI), bis-maleimide (BMI), epoxy, phenolic polymers (e.g., polystyrene), polyesters, polyurethanes, silicone rubbers, and combinations thereof.
 6. The article of claim 1, wherein the metallic nano-crystalline coating comprises: a first layer comprising nano-crystalline cobalt defining a first thickness; and a second layer comprising nano-crystalline nickel defining a second thickness, wherein the first thickness is greater than the second thickness.
 7. The article of claim 1, wherein the article comprises an aerospace component comprising at least one of a rotor, a disc, a turbine blade, a housing element, a bracket, a chevron ventilation outlet, a vane box plume tab, a variable vane actuator arm, a nose cone, an airfoil, a flap, an accessory gear, or an air-flow surface.
 8. The article of claim 1, further comprising a metal-polymer laminate on the polymer-based substrate, wherein the metal-polymer laminate comprises: a first metallic nano-crystalline layer comprising the metallic nano-crystalline coating; at least one polymer-based layer on the first metallic nano-crystalline coating; and a second metallic nano-crystalline layer on the least one polymer-based layer, wherein the second metallic nano-crystalline layer defines an average grain size less than about 20 nanometers.
 9. The article of claim 1, wherein the polymer-based substrate comprises a truss structure defining a plurality of truss supports.
 10. An article comprising: a polymer-based substrate; and a metallic nano-crystalline coating on at least a portion of the polymer-based substrate, wherein the metallic nano-crystalline coating defines an average grain size less than about 20 nanometers, wherein the portion of the polymer-based substrate has a first Young's modulus and the metallic nano-crystalline coating has a second Young's modulus, and wherein the first and second Young's modulus are selected to dampen a predetermined vibration frequency in the article.
 11. The article of claim 10, wherein the polymer-based substrate comprises a polymeric material and a plurality of reinforcement fibers embedded in the polymeric material.
 12. The article of claim 10, further comprising a dense core material, wherein the polymer-based substrate substantially surrounds the dense core material, and wherein the dense core material comprises a metal or a metal alloy having a density between about 2.5 grams per cubic centimeter (g/cm³) and about 9.0 g/cm³.
 13. The article of claim 10, wherein the metallic nano-crystalline coating comprises: a first metallic nano-crystalline layer defining a first thickness; and a second metallic nano-crystalline layer defining a second thickness, wherein the first thickness is different than the second thickness.
 14. The article of claim 11, wherein the metallic nano-crystalline coating comprises an overall thickness measured normal to an exterior surface of the polymer-based substrate, wherein the overall thickness is selectively varied on different regions of the polymer-based substrate.
 15. The article of claim 11, further comprising a metal-polymer laminate on the polymer-based substrate, wherein metal-polymer laminate comprises: a first metallic nano-crystalline layer comprising the metallic nano-crystalline coating; at least one polymer-based layer on the first metallic nano-crystalline coating; and a second metallic nano-crystalline layer on the least one polymer-based layer, wherein the second metallic nano-crystalline layer defines an average grain size less than about 20 nanometers.
 16. A method for forming an aerospace component comprising: forming a polymer-based substrate comprising a polymeric material; and depositing a metallic nano-crystalline coating on at least a portion of the polymer-based substrate, wherein the metallic nano-crystalline coating defines an average grain size less than about 20 nanometers, wherein the portion of the polymer-based substrate has a first Young's modulus and the metallic nano-crystalline coating has a second Young's modulus, wherein the first and second Young's modulus are selected to dampen a vibration in the article at a predetermined frequency.
 17. The method of claim 16, wherein forming a polymer-based substrate comprises embedding a plurality of reinforcement fibers in the polymeric material, wherein the plurality of reinforcement fibers are non-uniformly distributed in the polymer-based substrate.
 18. The method of claim 16, further comprising forming a dense core material comprising a metal or a metal alloy having a density of about 2.5 grams per cubic centimeter (g/cm³) and about 9.0 g/cm³, wherein the polymer-based substrate at least partially encases the dense core material.
 19. The method of claim 16, further comprising: depositing at least one polymer-based layer on the metallic nano-crystalline coating; and depositing at least one additional metallic nano-crystalline layer on the at least one polymer-based layer.
 20. The method of claim 16, further comprising selectively varying a thickness of the metallic nano-crystalline coating as measured normal to an exterior surface of the polymer-based substrate. 